[Solved] Need help finding where all my C: drive space has gone.

[ShadowScarify]

Every time I check how much space is left on my C drive, it seems to have haemorrhaged a little more free space. This is in spite of running CCleaner regularly, making sure it's not got excessive fragmentation, etc. I try to keep it as spartan as possible. I've looked for solutions all over and have done everything I can find to get that free space back, and yet it stills seems to leak away.

Not only that, but when I compare the size of the files on the disk, to how much room they are apparently taking up, the results don't add up... literally.
Using WinDirStat to look at the files on the C drive, it says that they take up approximately 100GB. But the drive (a 200GB partition) shows that over 190GB of space is being taken up.

Can anyone help me find where all the lost space is going and help me clean up my drive?

Screenshot:

UPDATE:
Opening up the Disk Management and right clicking the drive and looking at the properties from there seems to have "refreshed" the disk usage and now it's back down to where it should be. I don't have an explanation for why that happened though. Very strange.

 

[USAFRet]

The one big thing that WinDirStat misses is Restore points. And they can take up a lot of space, depending on your settings.

 

[ShadowScarify]

The one big thing that WinDirStat misses is Restore points. And they can take up a lot of space, depending on your settings.

This is true, by default. Which is strange since it'll get the page file and hibernation files.
Remember kids, when using WinDirStat, make sure to go to the Options tab and check "Show Unknown".

That was one thing I did make sure to check a while back. However, when I checked it again just now, the disk space usage for System Protection was set to 50%. 99GB. I don't know what the default it, but I'm pretty sure it's not that.

Unfortunately, now it says that the Current Usage is 0 bytes. And WinDirStat shows <Unknown> at 0 bytes too. Did all my restore points just vanish?

 

[USAFRet]

The one big thing that WinDirStat misses is Restore points. And they can take up a lot of space, depending on your settings.

This is true, by default. Which is strange since it'll get the page file and hibernation files.
Remember kids, when using WinDirStat, make sure to go to the Options tab and check "Show Unknown".

That was one thing I did make sure to check a while back. However, when I checked it again just now, the disk space usage for System Protection was set to 50%. 99GB. I don't know what the default it, but I'm pretty sure it's not that.

Unfortunately, now it says that the Current Usage is 0 bytes. And WinDirStat shows <Unknown> at 0 bytes too. Did all my restore points just vanish?

Depending on the system, the default may well be 50%.
If your current usage is now 0%, then yes, I believe your previous Restore points are gone.